text: /*=========================================================================
   *
   *  Copyright NumFOCUS
   *
   *  Licensed under the Apache License, Version 2.0 (the "License");
   *  you may not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *         http://www.apache.org/licenses/LICENSE-2.0.txt
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   *
   *=========================================================================*/
  #ifndef itkLaplacianOperator_hxx
  #define itkLaplacianOperator_hxx
  #include "itkLaplacianOperator.h"
  
  namespace itk
  {
  template <typename TPixel, unsigned int VDimension, typename TAllocator>
  void
  LaplacianOperator<TPixel, VDimension, TAllocator>::SetDerivativeScalings(const double * s)
  {
    for (unsigned int i = 0; i < VDimension; ++i)
    {
      m_DerivativeScalings[i] = s[i];
    }
  }
  
  // Create the operator
  template <typename TPixel, unsigned int VDimension, typename TAllocator>
  void
  LaplacianOperator<TPixel, VDimension, TAllocator>::CreateOperator()
  {
    CoefficientVector coefficients;
  
    coefficients = this->GenerateCoefficients();
  
    this->Fill(coefficients);
  }
  
  // This function fills the coefficients into the corresponding neighborhodd.
  template <typename TPixel, unsigned int VDimension, typename TAllocator>
  void
  LaplacianOperator<TPixel, VDimension, TAllocator>::Fill(const CoefficientVector & coeff)
  {
    typename Superclass::CoefficientVector::const_iterator it;
  
    std::slice * temp_slice;
    temp_slice = new std::slice(0, coeff.size(), 1);
  
    typename Self::SliceIteratorType data(this, *temp_slice);
    delete temp_slice;
  
    it = coeff.begin();
  
    // Copy the coefficients into the neighborhood
    for (data = data.Begin(); data < data.End(); ++data, ++it)
    {
      *data = *it;
    }
  }
  
  template <typename TPixel, unsigned int VDimension, typename TAllocator>
  typename LaplacianOperator<TPixel, VDimension, TAllocator>::CoefficientVector
  LaplacianOperator<TPixel, VDimension, TAllocator>::GenerateCoefficients()
  {
    unsigned int i, w;
  
    // Here we set the radius to 1's, here the
    // operator is 3x3 for 2D, 3x3x3 for 3D.
    SizeType r;
  
    r.Fill(1);
    this->SetRadius(r);
  
    // Create a vector of the correct size to hold the coefficients.
    w = this->Size();
    CoefficientVector coeffP(w);
  
    // Set the coefficients
    double sum = 0.0;
    for (i = 0; i < 2 * VDimension; i += 2)
    {
      OffsetValueType stride = this->GetStride(i / 2);
  
      const double hsq = m_DerivativeScalings[i / 2] * m_DerivativeScalings[i / 2];
      coeffP[w / 2 - stride] = coeffP[w / 2 + stride] = hsq;
      sum += 2.0 * hsq;
    }
    coeffP[w / 2] = -sum;
  
    return coeffP;
  }
  } // namespace itk
  
  #endif
  